The overall purpose of this study is to develop the neuroblast of the grasshopper embryo as a rapid and relatively inexpensive mutagen test system which can be used routinely as one of a battery of tests to screen chemical mutagens, carcinogens and teratogens. The neuroblast has almost no spontaneous chromosome aberrations and has been shown to be very sensitive to x-rays: aberrations and mitotic inhibition can be detected after 1 rad. Specific aims are: (1) to establish a breeding colony of Chortophaga viridifasciata in the lab for year-round supply of embryos; (2) determine frequencies of aberrations in neuroblasts of embryos exposed in vitro to a wide range of doses of some known chemical mutagens/carcinogens (direct acting and requiring metabolic activation) to compare sensitivity with other test systems; (3) determine effects of these agents on cell cycle kinetics, a component of teratogenesis; (4) test metabolic intermediates of some pharmaceuticals suspected of being mutagenic; (5) work out a banding method for the neuroblast chromosomes in order to localize hot spots of mutagen action; and (6) develop methods of separation of neuroblasts from embryos for in vitro determination of mutagen effects on reproductie integrity. It is our intention to determine in as much detail as possible the response of the neuroblast to a limited number of mutagens in order to gain basic information with which to evaluate the usefulness of this promising cell as a test system and which will be helpful in inerpreting mutagen action.